The present invention relates to a method and system for obtaining two or three-dimensional co-ordinate data in space and, more particularly, but not exclusively to a positional element and supporting hardware and software for obtaining such co-ordinate information. In general terms one unit is able to determine the position, typically in relation to itself, of another unit.
The field of small space positioning, that is positioning within spaces of a few meters or less, includes a number of fields, principally pointing devices for computer interaction, and robotics and machine control, but also including toys; inventory control and other fields. Certain applications may require 2D solutions, others may require 3D solutions. Again certain applications such as pointing devices may require only one-way communication, whereas say robotics may require two-way communication.
1) Pointing Devices.
Digital Pens:
Digital pens are pointing devices used for electronic detection of handwriting or hand drawing, or for general pointing. The digital pens generally use technologies such as acoustics, IR and light. Other versions use accelerometers that sense accelerations and transmit the data to a base station. Another version is a camera that analyzes small printing codes on special paper to determine its position. Other pens use electromagnetic (including passive & active), and other technologies for their operation. Some of the digital pens are an autonomous unit, meaning the pen works independently, providing its own fully processed co-ordinates as an output, and such is typical of optical and digital camera based units. Others, especially acoustic and electromagnetic devices, require a receiving or sensing unit.
Digital Pens are widely used with PC's, laptops, PDA's, cellular telephones, electronic books, and the like.
Interactive Whiteboards:
The interactive whiteboard is a whiteboard that captures written data from the board into an associated computer. One of the common technologies in this field is acoustic positioning: a marker is placed in a sleeve that transmits beacon signals which are picked up and analyzed by a dedicated device also placed near the whiteboard. In some cases an IR or electromagnetic signal is transmitted along with the acoustic beacon to for better accuracy and for simplicity. Another common technology is electromagnetic: the above mentioned marker sleeve transmits an electromagnetic field which is picked up by special loops on the back of the whiteboard.
Resistive technology is also used. In such a case the surface of the whiteboard is coated with resistive material. Pressure is applied to the coating, and the pressure causes a local change in the resistive properties of the board. From the changes, the controller is able to obtain an x, y position from the applied pressure.
Capacitive technology, which is similar to the resistive, can also be used. Again, pressure is used, this time to change the capacitive properties of the board. Then, the controller is able to obtain the x, y position
Touch Screens:
Touch screens generally comprise sensors embedded within or near a computer screen in order to receive input from the screen. Some technologies include coating the screen with special material that can sense physical contact, the material being any of resistive, capacitive and SAW material. Other technologies include embedding of sensors around the screen. The sensors may be IR, acoustic, SAW and others.
3-D Mouse:
A 3D mouse uses electromagnetic or ultrasonic positioning techniques to indicate its position in 3-D space to a monitoring device. The cordless mice in use today use BlueTooth and similar radio and IR transmitters for wireless connectivity. The radio or IR only takes care of the wireless connectivity, that is the signaling issue. Positioning generally involves a movement tracker in the mouse itself, which may be optically based. Simple movement tracking gives a 2D solution. 3D solutions can be produced, for example using either of the following:                1) acoustic: the mouse emits ultrasonic and IR pulses which are received by a desktop receiver. By measuring the time of flight, triangulation can be performed.        2) IR sensors: the mouse emits IR pulses whose angle is measured by a desktop receiver. Several angle sensors allow making 3-dimensional triangulation thus obtaining the special position.        
PC Tablets and Styluses:
The PC tablet uses a digital pen or stylus. The stylus enables interactions including writing directly on a graphic tablet, pc tablet, pc screen, pda screen, cell-phone screen and on any other computer enabled surface, screen or tablet. Available solutions work with passive or active electromagnetic or acoustic technologies.
Drawbacks
The solutions of the available technologies suffer from the following drawbacks. It is noted that these drawbacks are applicable to applications discussed below as well:
All of the solutions mentioned above require significant computation strength, and amplification and digitization circuitry. They do not utilize available resources of the main computer; instead they carry out their own calculations using dedicated hardware and feed the computer with the processed positioning data. The dedicated hardware is both expensive and complex, and is particularly wasteful of resources considering that the calculating power of the main computer is available.
All the technologies mentioned above, except the acoustic, need sensors on the positioning plane: the electromagnetic solution needs antenna loops on the back of the board, the pen with the camera needs special digitized paper and the touch-screens need special coatings. The need for sensors adds both to the cost of the final product, and furthermore provides an unnatural restriction on use in that it does not allow the user to use arbitrary planes, such as a cluttered desk surface, as a working platform.
The complex circuitry and sensors of these solutions require dedicated space. It is impossible to integrate the solutions to small and hand-held devices for which they have not been explicitly designed, such as PDA's, cellular phones etc. This issue is also significant with laptops and other movable products where the small size permits a fixed explicitly designed installation but does not allow for the freedom of an arbitrary device.
The installation of hardware components on a PC is tedious and not always reliable. It is significantly easier to use already installed components such as existing sound systems when adding a new feature.
There is no cross-platform solution currently available: a positioning solution for a touch screen is different from a digital pen solution for the mobile phone market, etc.
The integration of available solutions into an existing product is often ineffective, because of the size and the complexity of the project.
All the available solutions in fact require re-designing of the end product. There is no current solution that can be treated as add-in, requiring only software changes.
Support for multiple user applications is difficult and is currently only available where BlueTooth is the communication medium. Bluetooth is nevertheless restricted to eight simultaneous users.
Many of the available solutions require substantial power supply.
Some of the technologies are limited to two-dimensional location. But even those that can manage a third dimension do not currently provide accurate information of the third dimension. For example a stylus based on electromagnetic detection can be detected when hovering above a screen, but it is not possible to tell accurately how high it is. The detector simply determines that it is present.
There are other drawbacks specific to certain of the technologies. For instance, IR positioning has difficulties working with direct sun. Existing acoustic solutions have serious limitations in acoustically noisy environments, in particular in the all-important industrial environment, where ultrasound noise is most common.
Solutions that use wireless protocols as Bluetooth may suffer from protocol collisions, and from interference with other wireless equipment, such as WLAN equipment.
Touchscreen solutions are of course inherently two-dimensional.
2) Robotics and Machine Control
Robotics and Machine control is a field in which the use of position sensors is inherent to the control of moving elements.
Industrial Robots
Mechanical arms are able to perform delicate assembly tasks in 3-dimensional space. PCB assembly machines perform placement of electronic components on a 2-dimentional printed circuit board. CNC machines perform cut and drill tasks which need high position resolution. Automobile assembly lines use automatic drillers which drill the body of the car using high spacial accuracy.
Fax and Printer
Fax and printer machines have accurate position sensors for scanning, printing, paper orientation etc.
Freely Mobile Robots
In recent years several new robotics products have reached the prototype stage and beyond. The robotics products include freely moving robots for different applications. The applications include lawn mowers, pool cleaners, spy and bomb disposal robots with cameras and remote control and many more. Such robots typically use their own sensing together with pre-programming to find their way around in their surrounding environment.
Possible new applications include an autonomous vacuum cleaner. One or more vacuum cleaners may roam automatically around the premises, vacuuming dirt and transferring the dirt to either fixed location units or roaming units. The unit that vacuums may autonomously locate the receiving unit to which it delivers the dirt and dock therewith in order to deliver the dirt.
The sensors used in the robotics applications mentioned above use the following technologies:                1) Optical encoders: these sensors contain an enclosed rotating wheel with small holes on the perimeter of the wheel. An LED and a photosensor are mounted on either side of the wheel. As the wheel turns (due to the movement of the robot), the photosensor receives a series of light pulses. The light pulses encode the exact angle of the wheel, thus revealing the position of the moving arm. These sensors are also available as linear sensors, meaning that the sensor is not embedded on a rotating system but rather on a straight line.        2) Potentiometers: these sensors are attached in parallel to a moving object. The sensor changes its resistance as a function of its position.        3) LVDT: these are magnetic sensors which include 2 parts: an iron core and a magnetic cylinder. As the iron core moves inside the cylinder the magnetic properties of the cylinder change as a function of the position.        4) There are other, lesser used technologies of which the skilled person will be aware.        
All the technologies mentioned hereinabove in connection with robotics are relatively large scale. They all have to be attached one way or another to a moving part of the robot and there is no wireless solution that enables the attachment of a sensor on the tip of the moving arm/robot etc. As always, precision goes along with cost, making precision equipment costly. Sensors that have high precision over a few meters of distance can cost hundreds of thousands of dollars and are not economically viable for many of the envisaged uses of robots.
3) Toys
It is relatively uncommon, due to the high cost, to have toys in which one unit can be aware of the location of a second unit.
In a very basic example, one toy notes that there is another toy nearby, prompting a reaction, for example talking. In a more sophisticated example, one toy knows more or less where the other toy is.
In the future it is hoped to provide a yet more sophisticated example in which one unit can successfully pass an object to the next one and vice versa. Further in the future a toy is envisaged, in which twenty-two soccer robots run around passing the ball one to another. The robots calculate where to kick according to the locations of the other robots on the same and opposite teams. To provide each of the twenty robots with the computing and control power in order to play a game of soccer produces a very expensive and complex solution.
Generally, toy technology has to be provided at low cost and current technology is relatively expensive. Specific technologies each have their drawbacks:
Infrared sensors—IR can be used to indicate the presence in the vicinity of a second object. At a higher level it can show a general direction.
Accelometers—the disadvantages of accelerometers are discussed above in the section on pointing devices.
Acoustic—Acoustic devices are relatively expensive. Only a single unit can be used in the same environment, energy use is relatively high, and the devices are difficult to miniaturize.
There is thus a widely recognized need for, and it would be highly advantageous to have, a positioning system devoid of the above limitations.